The present invention relates to a fuser member and method for fusing toner images in an electrostatographic reproducing, including digital, apparatus. The present invention further relates to a method for preparation of such a fuser member. More specifically, the present invention relates to methods and apparatuses directed towards fusing toner images using a fuser member having a polymer layer with zinc compound dispersed or contained therein, and in preferred embodiments, the polymer and zinc compound layer is the outer layer of the fuser member. In a particularly preferred embodiment, the polymer/zinc compound fuser member outer layer is used in combination with functional release agents, and more specifically, amino functional release agents.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support which may be the photosensitive member itself or other support sheet such as plain paper.
The use of thermal energy for fixing toner images onto a support member is well known. To fuse electroscopic toner material onto a support surface permanently by heat, it is usually necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material cause it to be firmly bonded to the support.
Several approaches to thermal fusing of electroscopic toner images have been described. These methods include providing the application of heat and pressure substantially concurrently by various means, a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat may be applied by heating one or both of the rolls, plate members, or belt members.
It is important in the fusing process that minimal or no offset of the toner particles from the support to the fuser member take place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus increasing the background or interfering with the material being copied there. The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser, and accordingly it is desired to provide a fusing surface which has a low surface energy to provide the necessary release.
To ensure and maintain good release properties of the fuser, it has become customary to apply release agents to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils such as polydimethyl siloxane (PDMS), mercapto oils, amino oils, and other oils to prevent toner offset. The fuser oils may contain functional groups or may be non-functional.
Fillers have been added to the outer layer of fuser members in order to increase the bonding of the fuser oil to the surface of the fuser member to impart improved release properties.
U.S. Pat. No. 5,464,698 discloses a fuser member having a layer including a cured fluorocarbon random copolymer having subunits of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene, and having tin oxide fillers in combination with alkali metal oxides and/or alkali metal hydroxide fillers incorporated into the fuser layer. A polydimethylsiloxane release oil is disclosed.
U.S. Pat. No. 5,292,606 discloses a fuser roll having a base cushion layer comprising a condensation-crosslinked polydimethylsiloxane elastomer and having zinc oxide particles dispersed therein. A polydimethylsiloxane oil is also disclosed.
U.S. Pat. No. 5,464,703 discloses a fuser member having a base cushion layer including a crosslinked poly(dimethylsiloxane-fluoroalkylsiloxane) elastomer having tin oxide particles dispersed therein. A polydimethylsiloxane fuser oil is also disclosed.
U.S. Pat. No. 5,563,202 discloses a fuser member having a base cushion layer having a crosslinked poly(dimethylsiloxane-fluoroalkylsiloxane) elastomer having tin oxide particles dispersed therein. A polydimethylsiloxane fuser oil is also disclosed.
U.S. Pat. No. 5,466,533 discloses a fuser member having an overlying layer comprising a crosslinked polydiphenylsiloxane-poly(dimethylsiloxane) elastomer having zinc oxide particles dispersed therein. A polydimethylsiloxane fuser oil is also disclosed.
U.S. Pat. No. 5,474,852 discloses a fuser member having an overlying layer comprising a crosslinked polydiphenylsiloxane-poly(dimethylsiloxane) elastomer having tin oxide particles dispersed therein.
U.S. Pat. No. 5,480,724 discloses a fuser member having a base cushion layer comprising a condensation-crosslinked polydimethylsiloxane elastomer having tin oxide particles dispersed therein. A polydimethylsiloxane fuser oil is also disclosed.
U.S. Pat. No. 5,547,759 discloses a fuser member having a release coating comprising an outermost layer of fluoropolymer resin bonded to a fluoroelastomer layer by means of a fluoropolymer-containing polyamide-imide primer layer. Also disclosed is use of zinc oxide.
U.S. Pat. No. 5,595,823 discloses a fuser member having a layer including a cured fluorocarbon random copolymer having subunits of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene and having aluminum oxide filler along with alkali metal oxides and/or alkali metal hydroxide fillers incorporated into the fuser member layer. A polydimethylsiloxane and mercapto fuser oil are also disclosed.
U.S. Pat. No. 5,587,245 discloses a fuser member having an outer layer of an addition crosslinked polyorganosiloxane elastomer and zinc oxide particles dispersed therein. A polydimethylsiloxane fuser oil is also disclosed.
U.S. Pat. No. 5,531,813 discloses a polyorgano amino functional oil release agent having at least 85% monoamino functionality per active molecule to interact with the thermally stable FKM hydrofluoroelastomer surface of a fuser member. The patent discloses that no metal oxides are necessary to act as anchoring sites on the surface of the fuser member.
U.S. Pat. No. 5,516,361 discloses a T-type amino functional oil release agent having predominantly monoamino functionality per active molecule to interact with a hydrofluoroelastomer surface to provide release. The patent discloses that no metal oxides are necessary to act as anchoring sites on the surface of the fuser member.
It is important to choose the correct combination of fuser surface material, filler incorporated or contained therein, and fuser oil. Specifically, it is important that the outer layer of the fuser member react sufficiently with the selected fuser oil to obtain sufficient release. In order to improve the bonding of fuser oils with the outer surface of the fuser member, fillers have been incorporated into or added to the outer surface layer of the fuser members. The use of a filler can aid in decreasing the amount of fusing oil necessary by promoting sufficient bonding of the fuser oil to the outer surface layer of the fusing member However, it is important that the filler not degrade the physical properties of the outer layer of the fuser member, and further, it is important that the filler not cause too much of an increase the surface energy of the outer layer.
Other problems have resulted from use of fillers in that the oil may cause "gelling" or "scumming." "Gelling" or "scumming" is observed as whitish or grayish deposits on the fuser member surface left by paper debris as a result of its interaction with crosslinked fusing oil on the surface of the fuser member. The paper debris adheres to the fusing oil build-up and causes a "scum" or "gel" surface of the oil on the outer surface of the fuser member. The gelled or scummed areas on the fuser roll will attract toner particles leading to toner offset, and even in severe cases, to paper mis-strips or paper jams. "Gel" or "scum" forming on a fuser donor roll will lead to non-uniform oil application to the fuser roll and result in toner release problems such as toner offset, paper mis-strips and paper jams.
Another problem associated with the use of oils such as mercapto functional fusing oil, is the unpleasant odor produced by such oils. The use of mercapto oil, although providing sufficient toner release, has resulted in numerous and consistent customer complaints of foul odor.
Along with choosing the appropriate fusing oil in combination with the outer surface layer material and filler incorporated therein, efforts have been made to decrease the use of energy by providing a fuser member which has excellent thermal conductivity so as to reduce the temperature needed to promote fusion of toner to paper. This increase in thermal conductivity will also allow for increased speed of the fusing process by reducing the amount of time needed to sufficiently heat the fuser member to promote fusing. Efforts have also been made to increase the toughness of the fuser member layers in order to increase the layers' abrasion resistance and hence, the life of the fuser member.
Therefore, it is desirable to provide a fuser member having a combination of outer layer, filler and fusing oil, which decreases the occurrence of toner offset, gelling, scumming and adverse fusing oil odor. It is also desirable to provide a fuser member having an outer layer which provides for an increase in the fusing speed at a set temperature, or in the alternative, allows for use of a reduced temperature at normal or standard fusing speeds. It is further desirable to provide a fuser member which has an increased toughness in order to further the life of the fuser member.